BMI Calculator
Body Mass Index from weight and height, in kg/m².
How it works
BMI = weight(kg) ÷ height(m)²
BMI (Body Mass Index) divides weight by the square of height as a rough leanness measure. E.g. 65 kg at 1.7 m: BMI = 65 ÷ 1.7² ≈ 22.5.
Chinese adult cut-offs: <18.5 underweight; 18.5–23.9 normal; 24–27.9 overweight; ≥28 obese. BMI does not distinguish muscle from fat, so athletes may score high.
FAQ
What BMI is normal?
For Chinese adults, 18.5–23.9 is normal; 24+ is overweight and 28+ obese. Cut-offs vary by country/guideline.
What are BMI limitations?
BMI only uses the height-weight ratio; it cannot reflect body fat, muscle mass, or fat distribution, so it should not be the sole health conclusion.
Worked example
Height 1.75 m, weight 70 kg: BMI = 70 ÷ 1.75² = 70 ÷ 3.0625 ≈ 22.9. Against the Chinese adult bands (18.5–23.9 normal), this is normal.
At the same height, the healthy weight range is about 56.7–73.2 kg (18.5 × 3.0625 to 23.9 × 3.0625). At 78 kg the BMI would be ~25.5, entering the overweight band.
Notes and limitations
BMI only compares weight to height; it cannot separate muscle, fat and water. Regular lifters are often overestimated and older adults with muscle loss underestimated. Track waist circumference too (≥90 cm men, ≥85 cm women suggests central obesity) and watch the 3–6 month trend rather than a single reading.